Trimmer



Eem M, 3,956 M. .,s. SHAPP ET AL TRIMMER Filed Jan. 18, m54

United States Patent O TRIMMER Milton J. Shapp, Morton Station, and Henry J. Arbeiter,

Cornwells Heights, Pa., assiguors, by mesne assignments, to Jerrold Electronics Corporation, a corporation of Delaware Application January 18, 1954, Serial No. 404,623

4 Claims. (Cl. 317-249) Our invention relates to a trimmer condenser for use in conjunction with the invention of our previously filed patent application tiled July 8, 1953, Serial No. 366,642 for tuned electrical circuits wherein the signal is mixed to create a new frequency in order to reduce line losses.

In our prior filed application, we disclose a mixer wherein the circuit is brought into resonance by virtue of small tuning condensers.

The tuner must be not only readily adjustable, but must be able to withstand a wide range of temperature, through weather hazards such as rain and snow storms, and it must not be adversely affected by any chemicals in the air.

An object of our invention is to provide a trimmer body which has contact fingers that are adapted to engage the rotor for providing low inductive path for grounding the rotor.

Another object of my invention is to provide a small tuning condenser wherein the capacity must be changed from high to ultra high frequency along a smooth curve.

Other objects of our invention are to provide an improved device of the character described, that is easily and economically produced, which is sturdy in construction, and which is highly efficient in operation.

With the above and related objects in view, our invention consists in the details of construction and combination of parts, as will be more fully understood from the following description, when read in conjunction with the accompanying drawings, in which:

Fig. l is a sectional View of the trimmer taken along the line 1--1 of Fig. 4.

Fig. 2 is a perspective view of the main body of the trimmer.

Fig. 3 is an exploded view of the various elements making up the trimmer.

Fig. 4 is a complete assembled View of the trimmer.

Referring now in detail to the invention. wherein similar reference characters refer to similar parts, we disclose a trimmer wherein the range and capacity is from .5 mmf. to 6.5 mmf. with fourteen turns to cover the range and wherein there is an average of one and three quarters turns per mmf. This range of capacitance results in very smooth tuning control for very high and ultra high frequency ranges.

The trimmer comprises 'a main body, 4generally designated as A, having a cylindrical wall 10, which is threaded internally at 12 and externally at 14. The external threads 14 are adapted to receive a lock nut 16 which holds the unit on a suitable wall or surface. The end of the threads terminate adjacent a haxagon flange 18 which is integrally formed with the body A.

A plain cylindrical bore 20 is connected to the end of the thread 12 and the bore terminates within a conical wall 22. The inside conical wall 22 is made up of a plurality of internally and externally tapered fingers 24 for 2,774,017 y Patented Dec. 11, 1956 "ice receiving a teon insulator, generally designated as B, which ts over the conical extending fingers 24. An additional function of fingers will hereinafter be related. The teon insulator will not melt if it should come in con tact with hot solder.

The teflon insulator B has a cylindrical extension 26 and a bore 27 which is joined to the main body 28, and surrounding the extension 26 is a metallic cylinder, generally designated as C. A rotor or shaft, generally designated as D, has a threaded head 30 therein which fits within the threads 12, and a slit 32 on the outside of the head is for the purpose of receiving a screw driver tip or some other blunt instrument so that the head may be turned whereby the shaft 34 may be moved inwardly or outwardly within the bores 20, 22, and 27, the latter being the bore within the cylinder 26. lt should be noted that the capacitance can be greatly increased or decreased by virtue of the lengthy travel of the shaft D within the trimmer. Hence, to adjust the capacitance, the head 30 of the shaft D is turned inwardly or outwardly. The Q of the trimmer is essentially the same as the insulator teflon which is used and the Q is well over 2000.

The unit is particularly applicable for ultra high frequency and it produces a linear curve which is substantially a straight line for most of the turns. It is simple to use this trimmer to tune a co-axial cavity by removing the stator or outside plate and inserting the insulator directly into the end of a piece of tubing of .250 inch in internal diameter.

The plate tuner body and rotor is made of heavy brass which is silver plated to assure the lowest amount of inductance, and the construction of the contact fingers provides a direct low conductive path for grounding the rotor.

Although our invention has been described in considerable detail, such description is intended as being illustrative rather than limiting, since the invention may be variously embodied, and the scope of the invention is to be determined as claimed.

We claim as our invention:

l. A trimmer capacitor comprising a first conductive plate element comprising an elongated metallic body hav ing an internally threaded bore, a dielectric mounted on said rst conductive element, a second conductive plate element mounted on the dielectric, and a metallic plug threaded for a portion of its length and smooth and cylindrical for a portion of its length, and mounted inside the bore for controlled movement toward and away from the second plate element whereby the capacitance of the device may be varied, the plug being maintained in firm electric contact with the first plate element by spring contact at a point closer to the second plate element than the threaded contact, the spring contact being maintained between conductive contacts integral with the first plate element and the smooth portion of the plug.

2. A trimmer capacitor for providing smooth tuning capacitance control for very high and ultra-high frequency ranges comprising as a first conductor for the capacitor a metallic body, having a largely cylindrical internal bore extending through the body, internal threads in the top end of the bore, a plurality of tapered metallic fingers integral with the body and slanted inward and downward at the bottom of the bore to provide a frusto-conical opening in the bottom of the bore, a smooth metal plug in the bore having a diameter larger than the opening at the bottom of the fingers so that the fingers are in solid electric contact with the smooth plug when it is forced through the opening and an enlargement on the plug at its top 3 threaded to fit the internal threads of the bore; as a dielectric for the capacitor a sleeve of flexible dielectric material mounted on the metallic body and surrounding the iingers; and as a second conductor for the capacitor a metallic body mounted on the sleeve.

3. The invention of claim 2 wherein said insulator is of teflon and engages the ilexible ingers of said body, said insulator having a cylindrical end, and said second conductor embracing said secondv cylindrical end of said insulator.

4. The invention of claim 3 wherein said metallic and conductor members are silver plated.

References Cited in the le of this patent UNITED STATES PATENTS Ehlcrt Sept. 29, 1942 Becwar Oct. 4, 1949 Side Mar. 24, 1953 Bradburd May 4, 1954 Wagner Sept. 7, 1954 shun May 17, 1955 FOREIGN PATENTS Germany Apr. 10, 1941 

